1. Field of the Invention
The present invention relates to an image forming apparatus such as a facsimile, a copying machine or a printer.
2. Description of the Prior Art
In a facsimile using an electrophotographic system, the number of copies which can be outputted corresponding to the defined capacity of a developer (the capacity of a developer in a developer cartridge) has been previously set. The number of copies which can be outputted is generally set on the basis of a document having a standard black ratio (for example, 6%). The black ratio is the ratio of the number of black pixels to the total number of pixels per one document.
In practice, however, the black ratio of an image recorded by a facsimile is not necessarily a standard black ratio, thereby to make it difficult to estimate the number of copies which can be outputted. Therefore, it is also difficult to estimate the time when the developer is to be replenished.